With the recent introduction of high speed data into existing cellular network systems, such as Code Division Multiple Access (“CDMA”) 2000 and Wideband CDMA (“WCDMA”), two different data channels, specifically a high speed shared data channel and a low speed non-shared data channel, are available to mobile stations (“MSs”). As a result, the existing coding of the low speed data, using codes such as Walsh/Orthogonal Variable Spreading Factor (“OVSF”) codes, became shared resources between the low speed data and the high speed data.
These two data channels, however, consist of two very different data speed throughputs. Specifically, as an example, the high speed shared data channel (e.g., R5 of the Third Generation Partnership Project (“3GPP”)) can offer higher data speeds of up to 14 megabits per second (“mbps”) per user, while the low speed non-shared data channel (e.g., R99 of the 3GPP) offers only 384 kilobits per second (“kbps”). This discrepancy, however, is not efficiently accounted for because there is no defined partitioning guidance to transmit to the mobile station between the high speed shared data channel and the low speed non-shared data channel. Basically, where the same frequency carrier is shared between the two standards, the same OVSF resource is partitioned between the two services without any partitioning structure that accounts for the differences between the two standards.
Furthermore, since OVSF codes are typically allocated based on a code tree, a clearly cut boundary must be made during the transmission. This, however, greatly limits the high speed shared data channel's ability to manage its throughput because no mixed allocation guidance of the low speed data and the high speed data is available. As a result, as the code resource is limited in bandwidth, the inability to properly mix the allocation of the partitioned OVSF codes becomes a critical limiting factor when the high speed shared data channel is deciding to either maximize the number of users or to increase the peak user data rate. Thus, an inefficient code usage results between the two standards.
Moreover, since high speed data are shared on the high speed shared data channel, the shared channel scheduler will typically focus on the four best received users while other users may not be served for an extended period of time. As a result, some users fall between the cracks and are ignored unnecessarily because the scheduler fails to provide a loading pressure balance between the high speed data applications and the low speed data applications. Thus, the usage of the OVSF code resources is again not maximized, resulting in an inefficient use of the OVSF code resources. These problems are further exacerbated by the fact that the schedulers of the two standards are located at different components of the system. For example, the shared channel scheduler of the high speed data (e.g., R5) of the 3GPP is located at the base station (“BS”), whereas the low speed data scheduler of the low speed data (e.g., R99) is located at the radio network controller (“RNC”). This is problematic given that the OVSF codes are shared as a common resource between the BS and the RNC and the BS has no control over the RNC.
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